Microstrip-slotline Transition Research Articles

Miniaturized Single-Ended-to-Balanced Filtering Power Divider With High Selectivity Based on Tri-Mode Resonator

In this brief, a filtering power divider (FPD) based on a novel tri-mode resonator (TMR) is proposed firstly. Characteristic mode analysis (CMA) method is utilized to analyze the three modes of TMR in detail. Meanwhile, two transmission zeros (TZs) are generated due to TMR, which can improve the passband selectivity greatly. Then for the purpose of meeting the connecting requirement between single-ended and balanced components, a single-ended-to-balanced (SETB) FPD is realized on the basis of the FPD. In order to realize the miniaturization, a multilayer microstrip-slotline (M-S) transition structure is applied. As a result, the additional half-wavelength transmission slotline is not required. To validate the design method, the prototype has been manufactured and measured. The overall size is about 0.38 λg×1.04λg and the common-mode (CM) suppression level is better than 28.5 dB at all frequencies (the fractional bandwidth is 200%). Furthermore, the in-band insertion loss is lower than 1.2 dB and the isolation is higher than 17.6 dB in the passband.

High-Isolated Full-Duplex Dongle Antenna Based on Even-Mode Suppression for B5G Communications

A space-shared full-duplex antenna with high isolation is proposed for universal serial bus (USB) dongles. A compact antenna with a compact size of 22 mm x 4 mm comprises a loop and dipole antennas, working as a vertical monopole and a horizontal dipole, respectively. The dipole-type is fed by a microstrip-slotline transition with filtering characteristics of odd-mode bandpass and even-mode bandstop, avoiding the even-mode excitation for the loop antenna. The inherent isolation is caused by the orthogonality of the modes and the even-mode suppression (caused by the microstrip-slotline transition). Thus, high port isolation, low envelope correlation coefficients (ECC), and high efficiency are achieved across the 5G band of 3.4-3.6 GHz.

Optimization and Design of Balanced BPF Based on Mixed Electric and Magnetic Couplings

A balanced bandpass filter (BPF) with an improved frequency selectivity for differential-mode (DM) excitation and high rejection for common-mode (CM) excitation is proposed in this paper. Two half-wavelength stepped impedance resonators (SIRs) are employed based on mixed electric and magnetic couplings to realize a DM passband centered at 2.48 GHz. The center frequency and bandwidth can be easily controlled by optimizing the dimensions of SIRs and the coupling between them, respectively. Meanwhile, two transmission zeros (TZs) are generated based on the mixed electric and magnetic couplings and are independently controlled by tuning the coupling strength. Moreover, a wide DM stopband can be realized by optimizing the SIRs. The proposed balanced BPF is fed by balanced U-type microstrip–slotline transition structures, which can achieve high wideband CM rejection without influencing the DM responses, and the design complexity can be clearly reduced. Finally, a balanced BPF is fabricated, and a good agreement between the simulation and the measurement is observed, which verifies the design method.

Dual-Band Power Divider With Wide Passbands and Wide Harmonic Suppression Utilizing Multi-Mode T-Stub Loaded Slotline Resonators

This brief proposes a novel dual-wideband slotline power divider (DWSPD) with ultrawide stopband, which is suitable for the multi-band wireless communication system application. The proposed DWSPD is mainly constructed with two multi-mode T-stub loaded slotline resonators (MTSRs), four folded slotline structures (FSSs), four microstrip-slotline transitions and two isolation resistors. The MTSR can generate four transmission poles (TPs), which forms two wide passbands. Furthermore, the FSS contributes to four additional transmission zeros (TZs), which enhances the harmonic suppression. The fabricated DWSPD demonstrates the 3-dB fractional bandwidths of 45.3% @2.25 GHz and 47.1% @4.37 GHz and the stopband with a suppression more than 18 dB @ up to 40 GHz ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$17.8~f_{01}$ </tex-math></inline-formula> ). To the best of the author’s knowledge, the 3-dB FBWs and stopband achieve the best among the existing dual-band filtering power dividers (DBFPDs).

Design of a Novel Balanced-to-Balanced Dual-Band Diplexing Power Divider

In this brief, a balanced-to-balanced (BTB) dual-band diplexing power divider (DBDPD) implemented on a new asymmetric series T-junction MS transition is proposed. Firstly, a four-way BTB power divider (PD) as feed network was designed. The T-junction microstrip-slotline (MS) transitions are employed to realize phase shift and power division within a wide bandwidth. The balanced U-type MS transitions are adopted at each balanced port, which can realize superior common-mode (CM) suppression intrinsically while the differential-mode (DM) responses are independent. Then, the BTB DBDPD is realized by adding four pairs of step impedance resonators (SIRs) asymmetrically to the series T-junction. As a result, an asymmetric series T-junction MS transition with diplexing function is formed, which can flexibly adjust the operating passbands and adapt to the balanced port. Meanwhile, SIRs are employed to realize four sharp passbands. So as to verify the feasibility of the theoretical design, the proposed designs are manufactured. A good agreement can be observed between the simulation and measurement.

A balanced tri-band BPF with high selectivity based on ASSLR

Abstract In this paper, a balanced second-order tri-band bandpass filter (BPF) with high selectivity is proposed. Three differential-mode (DM) passbands are formed by applying one pair of asymmetric short stub-loaded resonators (ASSLRs) and uniform impedance resonators (UIRs) into the design. Meanwhile, the frequencies and bandwidths of the DM passbands can be quasi-independently controlled by the lengths of resonators and the gaps between them. In addition, broadband common-mode (CM) suppression is achieved intrinsically without affecting the DM parts based on the U-type balanced stepped-impedance microstrip-slotline transition (BSIMST) structures, thereby simplifying the design procedure significantly. In order to validate the practicability, a balanced tri-band BPF operating at 1.8, 3.5 and 4.45 GHz is fabricated and designed. A good agreement between the simulated and measured results is observed.

Broadband miniaturized 180° phase shifter based on symmetric coupling structure

An electronically reconfigurable wideband 180° phase switch using microstrip–slotline transitions is proposed. Multilayer structure with microstrips on the bottom and top layers, slotline on the middle layer confirm the broadband transmission. Taking advantage of the symmetry of the transition, only two p–i–n diodes are integrated on the top microstrip layer to achieve a 0°/180° phase reconfiguration. Miniaturized design is achieved with a size of 0.26λg × 0.16λg. The measured results are in good agreement with the simulated results, which show less than 5° phase deviation and less than 1.5 dB insertion loss across the band 0.68–2.5 GHz.

A balanced dual-band BPF with quasi-independently tunable center frequency and bandwidth

Abstract By introducing an open stub loaded resonator (OSLR) and a uniform impedance resonator (UIR) into balanced stepped-impedance microstrip-slotline transition structures, a balanced dual-band bandpass filter (BPF) with high selectivity and low insertion loss performance is presented in this paper. The balanced microstrip-slotline transition structures can achieve a wideband common-mode (CM) suppression. Meanwhile, the differential-mode (DM) passbands are independent from the CM responses, which greatly simplifies the design procedure. In addition, four varactors are loaded into OSLR and UIR to achieve the electrical reconfiguration. The proposed balanced dual-band BPF can realize quasi-independently tunable center frequencies and bandwidths. In order to verify the feasibility of the proposed design method, a prototype circuit of the proposed reconfigurable balanced dual-band BPF is simulated, fabricated and measured. A good agreement between the simulation and measurement results is observed.

A balanced ultra‐wideband bandpass filter based on H‐type sandwich slotline

In this paper, a balanced ultra-wideband (UWB) band-pass filter (BPF) with compact size and simple structure is proposed. The proposed filter is fed by microstrip-slotline transition structures. A UWB differential-mode (DM) passband is achieved by employing H-type sandwich slotline structure. The fractional bandwidth of proposed balanced BPF could reach as much as 132%. In order to improve the selectivity, a source-load coupling is introduced. Meanwhile, one more layer of substrate is employed to reduce the DM passband insert loss. In addition, due to the symmetrical structure, a high UWB common-mode suppression without influencing the DM passband is realized. Therefore, the filter design method can be simplified significantly. In order to validate the effectiveness of the design method, a balanced UWB BPF is fabricated and the simulated results agree well with the measured ones.

High Selectivity Dual-Wideband Balun Filter Utilizing a Multimode T-line Loaded Middle-Shorted CSRR

This brief presents a dual-band balun filter based on a novel slotline multi-mode T-line loaded middle-shorted complementary split-ring resonator (TLMS-CSRR) with wide bandwidth and high selectivity. Coupled with ${{\tau }}$ -shaped and ${{\pi }}$ -shaped slotline stub as input and output microstrip-slotline transition structure respectively, high rejection between two passbands and at harmonic frequencies are realized. With the TLMS-CSRR, the proposed balun filter obtains five transmission poles (TPs) and four transmission zeros (TZs) which broaden the bandwidth and sharpen the roll-off skirt significantly. Besides, a high-Q folded slotline coupled with input feeding line is introduced in ${{\tau }}$ -shaped structure to enhance the quality factor of TZ, resulting in more than 16 dB suppression between passbands. The ${{\pi }}$ -shaped slotline structure enhances harmonic rejection by 15 dB@ up to $8.7{f} _{1}$ (2.3 GHz). The fabricated balun filter demonstrates two passbands operating from 1.9 GHz to 2.7 GHz and 4.8 GHz to 5.6 GHz respectively. The measured magnitude imbalances are 0.4 dB and 0.6 dB while phase imbalances are 2.5° and 3°.

A tunable balanced dual‐band BPF with quasi‐independently controlled center frequency and bandwidth

In this paper, a balanced dual-band bandpass filter (BPF) with high selectivity and low insertion loss performance is presented by employing stub loaded resonators (SLRs) and stepped impedance resonators (SIRs) into balanced microstrip-slotline (MS) transition structures. The balanced MS transition structures can achieve a wideband common-mode (CM) suppression which is independent of the differential-mode (DM) response, significantly simplifying the design procedure. Six varactors are loaded into the resonators to achieve the electrical reconfiguration. The proposed balanced dual-band BPF can realize quasi-independently tunable center frequencies and bandwidths. A tuning center frequency from 2.48 to 2.85 GHz and a fractional bandwidth (20.16%-7.02%) with more than 15 dB return loss and less than 2.36 dB insertion loss are achieved in the first passband. The second passband can realize a tuning center frequency from 3.6 to 3.95 GHz with more than 12 dB return loss and less than 2.38 dB insertion loss. A good agreement between the simulated and measured results is observed.

Balanced-to-Single-Ended Four-Way Out-of-Phase Power Divider and Its Application to Broadband Balanced Quasi-Yagi Antenna Array

A broadband balanced-to-single-ended (BTSE) four- way power divider (PD) with out-of-phase is designed in this letter. The proposed four-way PD composed of three-series T-junction PDs, a balanced U-type microstrip-slotline transition structure, and multiple cross-junction microstrip-slotline transitions. The series T-junction PD achieves equal amplitude and out-of-phase power distribution at the output ports over a wide frequency band. Meanwhile, the balanced U-type structure as the feed of the BTSE PD can realize a great broadband common-mode (CM) rejection without affecting the differential-mode (DM) responses. In addition, the proposed BTSE PD is employed with four quasi-Yagi antennas to realize a balanced quasi-Yagi antenna array. The proposed antenna array keeps the merits of wide DM transmission and high CM suppression level and achieves low cross-polarization level and high gain in the endfire direction. Finally, a prototype antenna array is fabricated and measured, and the experimental results show that it exhibits 10 dB return loss bandwidth of 5.7-8.9 GHz, peak gain of 12.5 dBi, and maximum cross-polarization levels of -25.6/-34.6 dB in E-/H-planes at 5.8 GHz, respectively.

High selectivity and common‐mode suppression balanced bandpass filter with TM dual‐mode SIW cavity

Here, a compact balanced bandpass filter (BPF) with high selectivity and good common-mode (CM) suppression is proposed by adopting the TM dual-mode substrate integrated waveguide (SIW) cavity. The SIW cavity is connected to the input and output by the way of microstrip-slotline transition. Under differential-mode (DM) operation, two TM modes (TM 120 , TM 210 ) of the SIW cavity can be effectively excited, and simultaneously two transmission zeros (TZs) can be generated near the passband edges. Meanwhile, by designing the rotation angle and size of coupling slots reasonably, the deep stopband performance can be realised over a wide frequency range. Furthermore, the CM signal is effectively rejected because the magnetic current cannot be transferred to the coupling slot from the virtual open-ended microstrip feedline. Finally, a compact balanced BPF prototype for WLAN application has been designed and fabricated. Good agreement between simulated and measured results is obtained.

A highly selective balanced wideband bandpass filter based on nested split‐ring resonators

A balanced wideband bandpass filter (BPF) with a high frequency selectivity, controllable bandwidth, and good common-mode (CM) suppression based on nested split-ring resonators (SRRs) is proposed in this article. The proposed nested SRRs are applied to form three transmission poles (TPs) that can achieve a wide differential-mode (DM) passband centered at 3.0 GHz. Meanwhile, two transmission zeros (TZs) are generated to realize a high frequency selectivity of the DM passband. Moreover, TPs and TZs can be quasi-independently controlled by changing the physical lengths of SRRs and the gaps between them, which can greatly improve the flexibility and practicality of the design. The proposed balanced BPF is fed by balanced microstrip-slotline (BMS) transition structures. For the CM signals, the BMS transition structures can achieve a good wideband CM suppression without affecting the DM ones, thereby simplifying the design procedure. In order to validate its practicability, a balanced wideband BPF is fabricated and a good agreement between the simulated and measured results is obtained.

A balanced dual‐band BPF with independently controllable frequencies and bandwidths

A balanced second-order dual-band bandpass filter (BPF) with independently controllable center frequencies and bandwidths based on coupled stepped-impedance resonators (SIRs) is designed in this article. To obtain a dual-band differential-mode (DM) response, two pairs of SIRs with different resonant frequencies are employed in the design. The bandwidths of the two DM passbands can be independently tuned by adjusting the coupling gaps and coupling lengths of the corresponding resonators. In addition, three transmission zeros are realized to enhance the selectivity of the DM passbands. The microstrip-slotline transition structure is utilized to achieve a wideband common-mode (CM) suppression. Moreover, the DM responses are independent of the CM ones, which significantly simplify the design procedure. Finally, a balanced dual-band BPF is designed to validate the design method and a good agreement between the simulated and measured results is observed.

Compact Balanced Single-Band and Dual-Band BPFs with Controllable Bandwidth Using FoldedS-Shaped Slotline Resonators (FSSRs)

Abstract In this paper, two compact balanced bandpass filters (BPFs) using half-wavelength folded S-shaped slotline resonators (FSSRs) are designed. The proposed FSSR is realized by extending and folding a traditional S-shaped slotline resonator, which can affect the internal coupling of resonator and reduce the size of the resonator. The balanced stepped-impedance microstrip-slotline transition structures are employed to generate a wideband common-mode (CM) suppression. The proposed filters can realize a single-band differential-mode (DM) bandpass response or a dual-band one by employing one or three FSSRs, respectively. Moreover, the center frequencies of the DM passbands are independent from the CM responses, which can simplify the designs procedure significantly. In order to validate their practicability, a compact balanced dual-band BPF with controllable center frequencies and bandwidths is fabricated and good agreement between the simulated and measured results is observed.

A Balanced Filtering Quasi-Yagi Antenna With Low Cross-Polarization Levels and High Common-Mode Suppression

A balanced planar quasi-Yagi antenna integrated with a bandpass filtering response is presented in this paper. The proposed balanced antenna consists of a balanced stepped-impedance microstrip-slotline transition structure, a driver dipole, a parasitic strip, and a bandpass filtering unit. A good differential-mode (DM) passband selectivity is formed by inserting a microstrip stub-loaded resonator (SLR) in the feed line of the quasi-Yagi antenna. This integration enables the antenna to achieve both compact size and high frequency selectivity. By controlling the dimensions of SLR, the central frequency and fractional bandwidth (FBW) can be easy to be adjusted. Meanwhile, the microstrip-slotline transition structure can achieve a good wideband common-mode (CM) suppression without affecting the DM ones, thus simplify the design procedure. The proposed antenna with low cross-polarization level and high CM rejection is found to be comparable to the conventional quasi-Yagi antenna. Furthermore, there are two radiation nulls on both sides of the passband to improve the selectivity effectively. In order to validate its practicability, the balanced antenna is designed and fabricated. The experimental results exhibit that the designed balanced filtering antenna features good filtering response, low cross-polarization level, and high CM rejection.

A Differential UWB Quasi-Yagi Antenna with A Reconfigurable Notched Band

Abstract A compact differential ultra-wide band (UWB) planar quasi-Yagi antenna is presented in this paper. The proposed antenna consists of a balanced stepped-impedance microstrip-slotline transition structure, a driver dipole and one parasitic strip. A wide differential-mode (DM) impedance bandwidth covering from 3.8 to 9.5 GHz is realized. Meanwhile, a high and wideband common-mode (CM) suppression can be achieved by employing the balanced stepped-impedance microstrip-slotline transition structure. It is noted that the DM passband is independent from the CM response, which can significantly simplify the design procedure. In addition, a reconfigurable sharp DM notched band from 5.6 to 6.7 GHz is generated by adding one pair of quarter-wavelength varactor-loaded short-circuited stubs adjacent to the microstrip line symmetrically. In order to illustrate the effectiveness of the design, two prototypes of the antennas are designed, fabricated, and measured. A good agreement between the simulated and measured results is observed.

A balanced dual-band bandpass filter with independently tunable differential-mode frequencies

A balanced dual-band bandpass filter (BPF) with independently tunable differential-mode (DM) frequencies is proposed in this letter. The proposed BPF is composed of complementary split-ring resonators (CSRRs) etched on the ground and varactors loaded on the resonators. A balanced stepped-impedance microstrip-slotline transition structure is introduced to transfer the DM signals successfully and block the common-mode (CM) signals transmission. Good DM transmission and CM suppression can be achieved. Moreover, by changing the reverse bias voltages of the varactors loaded on coupling CSRRs, two DM resonant frequencies of the proposed balanced BPF can be tuned independently. To verify the feasibility of the design method, a balanced BPF with DM frequency ranging from 0.80 GHz to 1.12 GHz and 1.55 GHz to 2.05 GHz is fabricated and measured. Good agreement between the simulation and measurement results demonstrate the validity of the design.

A Balanced Tri-band PD Based on Microstrip-slotline Transition Structure Embedded Complementary Split-ring Resonators

AbstractA balanced tri-band equal power divider (PD) is proposed based on a balanced stepped-impedance microstrip-slotline transition structure in this paper. Multi-band differential-mode (DM) responses can be realized by embedding multiple complementary split-ring resonators (CSRRs) into the slotline resonator. It is found that a high and wideband common-mode (CM) suppression can be achieved. Moreover, the center frequencies of the DM passbands are independent from the CM ones, which significantly simplifies the design procedure. In order to validate its practicalbility, a balanced PD with three DM passbands centred at 1.57, 2.5 and 3.5 GHz is fabricated and a good agreement between the simulated and measured results is observed. To our best knowledge, a balanced tri-band PD is the first ever reported.